1. Field of the Art
The present invention relates to a condenser for a refrigerator and a method of operating the condenser. More particularly, the present invention relates to washing of heat exchanger tubes in such a condenser and also to the control of the flow rate of cooling water in the heat exchanger tubes.
2. Prior Art
In general, the following problems are known with regard to condensers used in refrigerators:
1. When scale from cooling water accumulates on the inner surface of heat exchanger tubes of the condenser, heat transfer is obstructed, and pressure in the condenser rises. In such a case, the following problems arise:
(1) Rise in the operating cost PA1 (2) Damage to equipment due to the occurrence of a surging operation or vibration in the case of a centrifugal refrigerator PA1 (3) Occurrence of a high pressure trip due to the operation of a pressure upper-limit switch
2. If the temperature of cooling water supplied to the heat exchanger tubes is low, the pressure in the condenser becomes excessively low.
In this case, since the required functions are generally obtained by making use of the pressure difference between the condenser and the evaporator, the following problems arise:
(1) The performance of a refrigerant-cooled oil cooler is lowered, resulting in a rise in the temperature of oil for lubrication.
(2) Because a refrigerant-cooled compressor motor cannot sufficiently be cooled, the coil of the motor overheats.
(3) The performance of an ejector type oil recovery system for recovering lubricating oil that has leaked into the refrigerant system is lowered.
(4) Circulation of refrigerant liquid through the refrigerator deteriorates.
In particular, when well water or river water is used as a cooling water, scale or slime rapidly accumulates on the inner surface of the heat exchanger tubes, and since the cooling water temperature is relatively low, the formation of scale or slime is accelerated.
Thus, in order to avoid these problems, it is necessary to periodically clean the inside of the heat exchanger tubes on the one hand, and to control the pressure of the condenser in a predetermined range during operation on the other hand.
To this end, heretofore, the cleaning of the heat exchanger tubes is effected by travelling a brush inside each tube while changing the direction of the flow of the cooling water in the heat exchanger tubes by means of a change-over valve.
Also, the condenser pressure is controlled by controlling the temperature or volume of the cooling water to be supplied to the heat exchanger tubes by controlling a throttle of a two-way valve in a cooling water supply pipe, by controlling a throttle of a three-way valve for controlling a volume of the cooling water bypassing a cooling tower or radiator and returning to the heat exchanger tubes, or by controlling a pump motor speed of a cooling water supply pump by means of an inverter.
However, all of these prior art arrangements require use of a two-way valve, a three-way valve or a pump speed control means in addition to the change-over valve and, therefore, the cost of the arrangement becomes relatively expensive. Also, when cleaning the heat exchanger tubes by means of a brushes, the volume of cooling water must be increased. Thus, such two-way valve or three-way valves must be manually or automatically opened, which is either a troublesome operation or requires the installation of an expensive control means.